High performance low cost monopole antenna for wireless applications

Abstract

A monopole antenna, a monopole antenna system and a data communication device are disclosed in which a high isotropic radiation characteristic is achieved with a minimum substrate area occupied by the antenna. To this end, a substantially T-shaped monopole design is used, wherein end portions of one of the resonating paths are oriented in conformity with respective edges of a substrate.

1. A printed monopole antenna, comprising:
 a substrate having a first surface and an opposed second surface; 
 an elongated first resonant portion formed on said first surface and defining a first axis in a longitudinal direction; 
 a second resonant portion formed on said first surface and having a center piece, defining a second axis, and first and second elongated end pieces forming an angle with said second axis, said second resonant portion extending from said first resonant portion, wherein said second axis is positioned at an angle with said first axis and an outer edge of each of said first and second end pieces is disposed proximate respective edges of said substrate; and 
 a ground plane formed on said second surface. 
 
     
     
       2. The printed monopole antenna of  claim 1 , wherein said second resonant portion is symmetric with respect to said first axis. 
     
     
       3. The printed monopole antenna of  claim 2 , wherein the outer edges of said first and second end pieces are substantially parallel to respective edges of said substrate. 
     
     
       4. The printed monopole antenna of  claim 2 , wherein outer edges of said first and second end pieces are oriented to each other in a substantially perpendicular fashion. 
     
     
       5. The printed monopole antenna of  claim 2 , wherein said second axis is substantially orthogonal to said first axis. 
     
     
       6. The printed monopole antenna system of  claim 1 , wherein said first and second end portions are tapered. 
     
     
       7. A printed monopole antenna system, comprising;
 a substrate having opposed surfaces; 
 a first monopole antenna formed on one of said opposed surfaces and having a first elongated resonant portion and a second resonant portion extending from said first elongated portion to form an angle with a first axis extending along the longitudinal direction of said first resonant portion, said second resonant portion being symmetric with respect to said first axis; 
 a second monopole antenna formed on one of said opposed surfaces having a second elongated portion defining a second axis that forms an angle with said first axis; 
 a first ground plane formed on the other one of said opposed surfaces on which said first monopole antenna is formed; and 
 a second ground plane formed on the other one of said opposed surfaces on which said second monopole antenna is formed. 
 
     
     
       8. The printed monopole antenna system of  claim 7 , wherein said second monopole antenna is identical in configuration to said first monopole antenna. 
     
     
       9. The printed monopole antenna system of  claim 7 , wherein said second resonant portion comprises an elongated center portion extending from said first resonant portion, and first and second end portions connected to said center portion, said first and second end portions forming an angle with said center portion. 
     
     
       10. The printed monopole antenna system of  claim 9 , wherein an outer edge of said first and second end portions are substantially orthogonal to each other. 
     
     
       11. The printed monopole antenna system of  claim 7 , wherein said first and second ground planes form a continuous conductive area. 
     
     
       12. The printed monopole antenna system of  claim 7 , wherein said first ground plane has a first edge that is substantially perpendicular to said axis of said first monopole antenna. 
     
     
       13. The printed monopole antenna system of  claim 12 , wherein said second ground plane has a second edge that is substantially perpendicular to said second axis of said second monopole antenna. 
     
     
       14. The printed monopole antenna system of  claim 7 , wherein said first axis is substantially perpendicular to said second axis. 
     
     
       15. The printed monopole antenna system of  claim 7 , wherein said first and the second monopole antennas are formed on said first surface. 
     
     
       16. The printed monopole antenna system of  claim 9 , wherein said first and second end portions are tapered. 
     
     
       17. A data communication device, comprising:
 a substrate having a first surface and an opposed second surface; 
 a first printed monopole antenna comprising:
 an elongated first resonant portion formed on said first surface and defining a first axis in a longitudinal direction; 
 a second resonant portion formed on said first surface and having a center piece defining a second axis and first and second elongated end pieces forming an angle with said second axis, said second resonant portion extending from said first resonant portion, wherein said second axis is positioned at an angle with said first axis and an outer edge of each of said first and second end pieces is disposed proximate respective edges of said substrate; and 
 a ground plane formed on said second surface; and 
 
 a drive circuit formed on said substrate, said drive circuit being connected to said first printed monopole antenna. 
 
     
     
       18. The data communication device of  claim 17 , wherein said second resonant portion is symmetric with respect to said first axis. 
     
     
       19. The data communication device of  claim 17 , wherein the outer edges of said first and second end pieces are substantially parallel to respective edges of said substrate. 
     
     
       20. The data communication device of  claim 18 , wherein outer edges of said first and second end pieces are oriented to each other in a substantially perpendicular fashion. 
     
     
       21. The data communication device of  claim 17 , wherein said second axis is substantially orthogonal to said first axis. 
     
     
       22. The data communication device of  claim 17 , further comprising a second printed monopole antenna having a second orientation that differs from a first orientation of said first monopole antenna. 
     
     
       23. The data communication device of  claim 22 , wherein said second monopole antenna is substantially identical in configuration to said first monopole antenna. 
     
     
       24. The data communication device of  claim 23 , wherein said first orientation and said second orientation are substantially orthogonal to each other. 
     
     
       25. The data communication device of  claim 17 , further comprising a comparator circuit connectable to said first and second monopole antennas and configured to compare a first signal level obtained from said first monopole antenna with a second signal level obtained from said second monopole antenna. 
     
     
       26. The data communication device of  claim 25 , further comprising a switching circuit connected to said first and second monopole antennas, said comparator circuit and said drive circuit, said switching circuit being configured to selectively connect said first or second monopole antennas to said drive circuit upon a result from said comparator circuit. 
     
     
       27. The data communication device of  claim 17 , wherein said first and second end portions are tapered.